Electrically-powered vehicles (EVs), such as hybrid electric vehicles (HEVs), plug-in hybrid vehicles (PHEVs), and battery electric vehicles (BEVs), have many advantages over vehicles powered by internal combustion engines (ICEs). For example, EVs may be more energy efficient and more environmentally friendly as they produce fewer emissions. An EV may include an electric motor for driving the gearbox and wheels, and the electric motor may be powered by batteries that may be recharged by plugging the vehicle into an electrical power source external to the vehicle, such as an electric outlet. EVs are associated with a driving range which is the distance that the EV may travel before the batteries are depleted and recharging is required. For example, driving ranges for current EVs may be on the order of about 80-300 miles. A plug-in hybrid electric vehicle (PHEV) is a type of EV that includes a small ICE and a fuel tank in addition to the electric motor and batteries. For example, the internal combustion engine may combust fuel to drive the vehicle at high speeds, such as on freeways or open roads, while the electric motor may drive the vehicle on city streets.
However, unlike ICE-powered vehicles in which heat from the ICE may be tapped to heat the passenger cabin, EVs may not have an ICE to use as a heat source and so require auxiliary heating sources. For example, some heating, ventilation, and air-conditioning (HVAC) systems in EVs use electrically-powered heaters that rely on battery power. The power load on the batteries to support the energy needs of the HVAC system may significantly reduce the driving range of the EV. In particular, substantially more battery power is needed to heat the passenger cabin up from a cold temperature to a warm temperature than is needed to maintain the passenger cabin at the warm temperature. To reduce battery power losses associated with initial heating, many EVs allow the driver to program the vehicle to pre-condition the passenger cabin to a comfortable temperature while the vehicle is parked and recharging at the electrical outlet. As a result, the energy requirement to heat the passenger cabin up from a cold temperature is supplied by the electric outlet, thereby reducing the power load on the batteries.
In another effort to reduce the power load on EV batteries for cabin heating, U.S. Patent Application Publication No. 2014/0208789 discloses the use of a phase change material (PCM) positioned about the vehicle battery to store heat from the battery during charging. In addition, a coolant circuit takes heat from PCM to heat the passenger cabin while driving. While effective, further heating system improvements for EVs are still wanting.
Clearly, there is a need for improved HVAC designs for EVs that reduce power loads on the batteries.